Many firearms, such as rifles, are equipped with an optical aiming device, such as a rifle scope, that provides the user with an image of an aligned aiming point or pattern (commonly known as a reticle) superimposed at the same focus as the target.
When shooting at long distances, shooters must adjust their aim to take into account the downward acceleration on the projectile imparted by gravity, which is often referred to as “bullet drop.” In some instances, this is done by adjusting the angular position of the optics of the rifle scope relative to the rifle barrel using an elevation turret. Similarly, a shooter may also adjust for left-to-right movement due to wind using a windage turret.
Additionally, the optical aiming device can be outfitted with a ballistic drop compensation (“BDC”) reticle that includes a reticle pattern for assisting a shooter to predict bullet drop at various ranges. The reticle can include a pattern with several different holdover marks stacked vertically beneath a central dot or crosshair which represents a zero mark. As such, when a firearm is zeroed to a certain range at the central crosshair, the stacked holdover marks will correspond to the bullet's impact at longer ranges. Accordingly, a shooter can choose an aiming point corresponding to one of the holdover marks or a point in between.
Humidity, elevation, temperature, grain size, bullet velocity and other various factors affect the flight of a bullet and the amount of bullet drop. As such, fixed-position BDC holdover marks do not consistently represent ranges. Furthermore, depending upon the above factors, the ranges represented can vary significantly, requiring calibration and experience for a shooter to accurately predict bullet drop and to use the BDC reticle.
Previous attempts to provide a BDC reticle are shown and described in U.S. Pat. Nos. 7,703,679; 6,269,581; and in U.S. Pub. No. 2015/0247702; each incorporated by reference herein in their entirety.